Color television receiving system



March 22,1955 G. c. SZIKLAI 2,704,783

COLOR TELEVISION RECEIVING SYSTEM Filed Aug. 14, 1948 DEFLECT/M(MCI/17.6 i;

i Z; I j E 4/ 05. a 7 I 4%; DZ ma 4 49 WIRE 5% wet- 2 2? 2 air 7 M00DEFL C/MLIT INVENTOR l I 34111-- ficg (*1 WM United States Patent coLoRTELEVISION RECEIVING SYSTEM George C. Sziklai, Princeton, N. J.,assignor to Radio Corporation of America, a corporation of DelawareApplication August 14, 1948, Serial No. 44,323

9 Claims. (Cl. 1785.4)

This invention relates to television, and more particularly to receivingset arrangements for the reception of images in substantially theirnatural color.

In color television systems wherein image reproduction is accomplishedby positioning in registry a group of color component imagesrepresentative of selected component colors which together add toproduce a resultant image in substantially its natural color, the imageis broken down not only into its elemental areas but into independentsignal trains representative of each of the selected component colors ofthe image.

Heretofore the formation of images in substantially their natural colorhas been accomplished by the production of several independent componentcolor images to be optically combined on a projection screen. Such anarrangement is well shown and described in an article entitled AnExperimental Simultaneous Color Television System, beginning on page 861of the Proceedings of the Institute of Radio Engineers for September,1947. In this article referred to, particular attention is directed toPart III, beginning on page 871, wherein the popular trinoscope is shownand described.

Upon an examination of the description and theory of operation of thetrinoscope it will be readily understood that mechanical and opticalprecision is important to insure that the several images are projectedin registry on the image projection screen.

In order to overcome the relatively stringent requirements formechanical and optical registry, there has been proposed a system forthe reproduction of images in substantially their natural color whereincolored images are formed sequentially by cyclically altering theeffective velocity of the scanning cathode ray beam of a cathode rayimage producing tube in the region of the target area of the imageproducing device. Such an arrangement is shown and described in detailin the copending U. S. application of Vladimir K. Zworykin, Serial No.739,503, filed April 4, 1947, and entitled Kinescope for ColorTelevision Reception, now Patent No. 2,566,713 granted September 4,1951.

In my copending U. S. application entitled Kinescope for theReproduction of Color Images, Serial No. 41,294, filed July 29, 1948,now Patent No. 2,543,477 granted February 27, 1951, colored light isobtained by altering the effective velocity of the scanning cathode raybeam of a cathode ray image producing tube in the region of the targetarea by physically retarding the velocity of the electrons bypredetermined amounts by means of mechanical barriers or the like.

The copending applications referred to immediately above dependbasically in theory of operation on an electron penetration phenomenacovered very thoroughly in an excellent treatise on the subject writtenby H. Bethe entitled The Theory of Transmission of Fast Corpuscular RaysThrough Materials, which may be found in the Annalen Der Physik, vol. 5,1930, beginning on page 325.

In this paper, considering electrons as the particles, the ray equationmay be simplified to a form:

BX =K (a constant) where 2,704,783 Patented Mar. 22, 1955 m is the massof the electron 9.04 10- gram,

N is the number of atoms per unit volume of the material, and

B is the retardation factor of the material.

Mr. Bethe gives the values for the retardation factor B (Bremsvermogen)for several materials, such as 18.7 for aluminum, 48.4 for gold, etc.;considering that the energy released in the solid is it is easily seenthat unless u is considerably smaller than no, the energy of theelectron is going to be released beyond the layer (in this case theenergy will be absorbed by the glass support), since which is a functioncontaining a maximum.

Thus considering a layer of phosphor with a barrier of a given K valuebombarded with a beam of increasing velocity, at first the radiationwill be zero since the beam does not penetrate the phosphor, then at avalue K=vo most of the energy will be absorbed by the phosphor, beyondwhich the loss of velocity becomes smaller and the energy lost willshift beyond the phosphor.

It will be seen from the above discussion that contrary to the obviousconcept, the light radiation does not necessarily increase with thevelocity of the impinging electrons but reaches a maximum and then isreduced.

It will be seen, therefore, that differently colored lights may beproduced in a stacked or composite screen arrangement wherein thevelocity of the electrons traveling through the screen is controlled insuch a manner that its most efiicient light producing velocity will beat the location of the selected color light producing phosphor or at thephosphor with the properly chosen associated light filter.

This particular principle has, of course, been recognized heretofore forthe production of colored light by electron bombardment. An electronsensitive photograph plate may be found well shown and described, forexample, in the U. S. patent to E. G. Ramberg, No. 2,442,961, dated June8, 1948, wherein electrons at controlled velocities are made to impingeupon a layered screen. The velocities are so chosen that the maximumefliciency of each of two velocities produces a maximum of radiation inone of two selected component color light producing mediums.

According to this invention, a novel arrangement is provided for colorselection wherein, for example, in a system employing three simultaneoustype selected component color image representative signal trains, thereis provided a cathode ray tube having an electron gun, an intensitycontrol electrode, and an electron target which includes a color controlelectrode and an associated color light producing material for each ofthe selected color components. A three phase oscillator modulates theincoming signal trains and at the same time applies its three phasesignal to the color control electrodes. The deceleration of thebombarding electrons in the appropriate color light producing medium maytherefore be controlled to produce upon a scanning action an image insubstantially its natural color.

A primary object of this invention is to provide an improved system forthe production of colored light and colored images.

Another object of this invention is to provide for improved colortelevision image reproduction.

Another object of this invention is to provide a novel electron beamtarget and associated equipment for color television systems.

Other and incidental objects of the invention will be apparent to thoseskilled in the art from a reading of the following specification and aninspection of the accompanying drawing in which:

Figure 1 illustrates schematically this invention in one of its forms;

Figure 2 shows by block diagram the operation of this invention; and

Figure 3 is a graphicillustration of the operation of this invention.

Turning now in more detail to Figure 1, there is shown a cathode raytube 1 including an electron gun 3 for generating a stream of electronsin the usual manner. The cathode ray tube 1 includes horizontal andvertical deflecting coils 5 and 7 together with the associateddeflection circuits 9 which receive synchronizing information in theusual manner.

It is not intended to go into detail regarding the construction of tube1 and its associated beam generating and deflection means because sucharrangements are well known to the electrical and television art.

Except for the novel target arrangement of this invention indicatedgenerally by the reference character 11, the tube may take the form ofany conventional kinescope which is well described in the early articleentitled Description of an Experimental Television System and Kinescopein the Proceedings of the Institute of Radio Engineers for December,1933.

A television receiver arrangement employing a k1nescope is shown in U.S. reissue patent to Carlson, No. Re. 20700, granted April 19, 1938. Thedeflect1on and control circuits shown and described therein and in a U.S. patent to Tolson et al., No. 2,101,520, granted December 17, 1931, orin the U. S. patent to Vance, No. 2,137,039, granted November 15, 1938,may be employed in connection with the tube 1 of this invention.Synchronization may be maintained in accordance with the arrangementdisclosed and claimed in the copend1ng U. S. application of Wright etal. entitled Beam Deflection Control for Cathode Ray Devices, Serial No.699,536, filed September 26, 1946, now Patent No. 2,460,112 grantedJanuary 25, 1949. The various electrodes of the electron gun 3 (not allshown) of the tube 1 are to be supplied as usual with suitable operatingpotentials.

In accordance with this invention, screen 11 consists of a plurality ofparallel layers of different selected component color light producingmaterials whlch, in a three color additive system, may consist of a redlight producing phosphor 13, a blue light producing phosphor 15, and agreen light producing phosphor 17, enclosed by and separated byelectrically independent, conductive and transparent films 19, 21, 23and 25. Conductive film 19 need not necessarily be transparent and may,for example, take the form of the aluminized backing employed inmonochromatic kinescopes for the improvement of light efiiciency andreduction of halation.

For the purpose of explanation of the operation of this invention, thereis provided a source of potential 27 and switches 29, 31 and 33.

By applying a relatively positive potential to the conductive film orlayer 19, it will be seen that the electrons approaching layer 19 willprogress through the layer 19 into the red light producing medium 13. Ifswitch 29 is thrown to the right, as shown, a positive potential will beapplied to conductive layer 21. The electrons will therefore proceedthrough the red light producing medium without being retarded andtherefore lose little or no energy in the red light producing medium 13.The electrons will therefore proceed through conductive barrier 21 intothe blue light producing medium 15. If the switch 31 is positioned asshown to provide conductive layer 23 with a relatively negativepotential, the electrons will be retarded by reason of the electricfield in the area between conductor 21 and conductor 23 such that theywill lose their energy in the blue light producing layer and thus causea blue light to be produced. Substantially no electrons will proceedthrough conductor 23 to.

the green light producing medium 17 so that no green light will beproduced.

It will be seen, therefore, that any of the three selected componentcolor lights may be produced depending upon which of the several colorcontrol electrodes 21, 23 or 25 is made relatively negative to retardthe velocity of the electron steam.

Color control may therefore be had in the arrangement shown by applyingproper relative potentials to color control electrodes 21, 23 and 25.

Figure 2 shows in block diagram one arrangement suitable for employmentof this invention for the reception of a simultaneous type colortelevision signal.

In the particular form shown by the example in the drawing, thetelevision receiving antenna 41 9 9F 99 to a converter 43 which provideswide band intermediate frequency amplifier 45 with suitable energy.

The signal energy from the intermediate frequency amplifier 45 isdivided in accordance with color com ponent information in the severaldetectors 47, 49 and 51. The separation of the different component colorimage signals is quite well explained in the color television art and itis not intended here to go into detail regarding such operation, as itis not intended that any specific form should be employed in thepractice of this invention.

Thereis, however, an improved arrangement for the separation of imagesignals in accordance with their color representation in my copending U.S. application entitled Signal Separator, Serial No. 760,400, filed July11, 1947, now Patent No. 2,626,323 granted January 20, 1953, wherein anarrangement is disclosed to provide for efficient amplification ofindependent signal trains representing selected component colors of acomposite image signal. The combined signal trains are amplified to apredetermined level before separation, as may be accomplished in wideband IF amplifier 45, and then are amplified independently of oneanother such as may be accomplished in the channel amplifiers 53, 55 and57, designated in the drawing as the red, blue and green channelamplifiers.

After being detected in detectors 47, 49 and 51, the several componentcolor image representative signals are zlgen amplified in appropriatevideo amplifiers 59, 61 and In accordance with previously proposedsynchronizing arrangements, the synchronizing signal is included in thegreen signal channel and separated therefrom in sync separator 65 tofurnish horizontal deflection circuit 67 and vertical deflection circuit69 with synchronizing energy.

Tube 1 of Figure 2 contains the deflection coils 5 and 7 and providesfor electron beam deflection in the usual manner.

Cathode ray tube 1 is provided with an electron gun 3 which forms anelectron beam controllable in intensity by control electrode 71.

A three-phase oscillator 73 in the presently described form of theinvention provides an output signal having three phases of sinusoidal orsubstantially sinusoidal energy, as illustrated graphically in Figure 3.

One phase of three-phase oscillator 73 iscombined with the red imagerepresentative signals in modulator 75. Another phase of the three-phaseoscillator 73 is combmed with the blue image representative signal inmodulator 77. Likewise, still another phase of the output energy ofoscillator 73 is combined with the green image representative signals inmodulator 79.

Electrodes 21, 23 and 25 of image tube 1 of Figure 2 are also connectedto the three-phase oscillator 73.

In accordance with the explanation given for the operat1on of cathoderay tube 1 in connection with Figure 1 above, the cathode ray beamproduces a red light when electrode 21 is given a relatively negativepotential with respect to the potential of electrode 19. It will beseen, therefore, that by adjusting the bias potentials in modulators 7577 and 79 such that only one of the modulators passes slgnals at any onetime, they all pass signals in a rapidly recurring sequential manner sothat energy applied to control electrode 71 is representative of onlyone selected component color image at a time.

It follows that if color control electrodes 21, 23 and 25 are connectedand properly phased so that the time they receive a relatively negativepotential corresponds to the time that their designated color componentimage representative signal train is being applied to the intensitycontrol electrode 71, a multiple color image may be formed.

The rate of changing will depend upon the speed of three-phaseoscillator 73 which may, of course, be made to operate at elementalsequential frequency.

A further explanation of the operation of this invention may be made byreferring briefly to Figure 3, wherein a three-phase signal is appliedto both the modulators and their associated color control electrodes. Itwill be seen that if the bias on the modulators is properly arranged sothat the area in the curve of Figure 3 between lines A and B indicatesoperation of the various modulators, three separate signal trains willbe transmitted to control electrode 71 which take the form of thesignals shown graphically at the bottom of Figure 3.

By applying the three-phase energy to the color control electrodes 21,23 and 25, the time interval of red luminescence will correspond to thetime interval when a red representative signal is being applied tocontrol electrode 71. During the time interval that the blue colorcomponent electrode is given a relatively negative potential withrespect to the other color control electrodes, only the bluerepresentative signal is being applied to the control electrode 71.Likewise, during the time interval that the green color controlelectrode 25 receives a relatively negative potential, only the greenrepresentative signal train is applied to the control electrode 71.

Having thus described the invention, what is claimed is:

1. A color image reproducing system comprising in combination a cathoderay tube having an electron gun for generating an electron beam, anintensity control electrode for said electron beam, and an electrontarget including an electrically independent conductive color controlelectrode and an associated color light producing phosphor for each ofthe selected color components, a signal channel for each of a pluralityof selected component color representative signal trains, an oscillatorhaving a substantially sinusoidal output signal, the oscillator signalalso consisting of a number of phases equal in number to the number ofdifierent selected component colors, a connection between saidoscillator and each of said channels and its similarly color designatedcolor control electrode to apply one different phase to each of saidchannels and its similarly color designated color control electrode toactivate in synchronism each of said channels and its similarlydesignated color control electrode, said connections to said channelsarranged to produce a mixing of the selected color componentrepresentative signal and said oscillator output, and a connectionbetween said intensity control electrode and all of said signal channelsto develop a natural color image on said target area.

2. In a color television system employing three simultaneous typeselected component color image representativesignal trains, a colorimage reproducing system comprising m combination a cathode ray tubehaving an electron gun for generating an electron beam, an intensitycontrol electrode and a color control electrode for said electron beam,and an electron target including an associated color light producingphosphor for each of the three selected color components, a signalchannel for each of the three selected component color representativesignal trains, a three-phase oscillator, a signal mixer in each of sa dsignal channels, a modulating connection between said oscillator andeach of said mixers and its similarly color designated color controlelectrode to apply one different phase to each of said mixers and itssimilarly color designated color control electrode to simultaneouslyactivate similarly color designated channels and color controlelectrodes, said connections to said mixers arranged to produce a mixingof the selected color component representatlve signal and saidoscillator output, and a connection between said intensity controlelectrode and all of said signal channels to control the intensity ofsaid electron beam for developing on said electron target an image incolor.

3. In a color television system employing substantially red, blue andgreen component color image representative signal trains, a color imagereproducing system comprising in combination a cathode ray tube havingan electron gun for generating an electron beam, an intensity controlelectrode for said electron beam, and an electron target, a colorcontrol electrode and an associated color light producing phosphor foreach of the selected color components, a signal channel for eachselected component color representative signal train, a three-phaseoscillator, a signal mixer in each of said signal channels, a connectionbetween said oscillator and each of said channels and its similarlycolor designated color control electrode to apply one different phase toeach of said channels and its similarly color designated color controlelectrode and control similarly color designated channel and colorcontrol electrode in synchronism, said connections to said channelsarranged to produce a mixing of the selected color componentrepresentative signal and said oscillator output, and a connectionbetween said intensity control electrode and all of said signal channelsto provide a modulation of said intensity control electrode for theproduction of a natural color image.

4. A color image reproducing system comprising in combination a cathoderay tube having an electron gun for generating an electron beam, anintensity control electrode for said electron beam, a luminescenttarget, a color control electrode and an associated component lightproducing medium for each of the selected color components, a signalchannel for each of a plurality of selected component colorrepresentative signal trains, an oscillator having a substantiallysinusoidal output signal, the oscillator signal also consisting of anumber of phases equal in number to the number of different selectedcomponent colors, a signal mixer in each of said signal channels, aconnection between said oscillator and each of said channels and itssimilarly color designated color control electrode to applysimultaneously one different phase to each of said channels and itssimilarly color designated color control electrode, said connections tosaid channels arranged to produce a mixing of the selected colorcomponent representative signal and said oscillator output, and means toapply to said intensity control electrode signals representative of thebrightness of the elemental area under scansion to develop a naturalcolor image on said luminescent target.

5. In a color television system employing a plurality of selectedcomponent color representative signal trains, a color image reproducingsystem comprising in combination a cathode ray tube having an electrongun for generating an electron beam, an intensity control electrode forsaid electron beam and an electron target, a color control electrode andan associated color light producing phosphor for each of the selectedcolor components, a signal mixer for each selected component colorrepresentative signal train, an oscillator having a substantiallysinusoidal output signal, the oscillator signal also consisting of anumber of phases equal in number to the number of difierent selectedcomponent colors, a signal mixer in each of said signal channels, aconnection between said oscillator and each of said signal mixers andits similarly color designated color control electrode to apply onedifferent phase to each of said channels and its similarly colordesignated color control electrode, said connections to said channelsarranged to produce a mixing of the selected color componentrepresentative signal and said oscillator output, and means for applyingto said control electrode a combination of said component colorrepresentative signal trains to modulate said control electrode and forman image on said target.

6. In a color television system employing a plurality of selectedcomponent color representative signal channels, a color imagereproducing system comprising in combination a cathode ray tube havingan electron gun for generating an electron beam, an intensity controlelectrode for said electron beam, an electron target, a color controlelectrode and an associated color light producing phosphor for each ofthe selected color components, an oscillator having a substantiallysinusoidal output signal, the oscillator signal also consisting of anumber of phases equal in number to the number or" different selectedcomponents colors, a modulating connection between each phase output ofsaid oscillator and a difierent one of said signal channels to controlcolor selections, and a connection between said intensity controlelectrode and each of said channels to control image brightness.

7. In a color television system employing a plurality of simultaneoustype selected component color representative signal trains, a colorimage reproducing system comprising in combination a cathode ray tubehaving an electron gun for generating an electron beam, an intensitycontrol electrode for said electron beam, and a color producing electrontarget consisting of transparent conductive layers spaced by differentselected component color light producing phosphors, a signal channel foreach selected component color representative signal train, anoscillator, the oscillator signal consisting of a number of phases equalin number to the number of different selected component colors, a signalmixer in each of said signal channels, a connection between saidoscillator, each of said channels and its similarly color designatedcolor control electrode to apply one diiferent phase to each of saidchannels and its similarly color designated color control electrode,said connections to said channels arranged to produce a mixing of theselected color component representative signal and said oscillatoroutput, and a connection between said intensity control electrode andall of said signal channels at a point in said signal channels whichincludes both the image signals and said oscillator signals.

8. In a color television system employing a plurality of simultaneoustype selected component color representative signal trains, a colorimage reproducing system comprising in combination a cathode ray tubehaving an electron gun for generating an electron beam, an intensitycontrol electrode for said electron beam,-and a color producing electrontarget consisting of transparent conductive layers spaced by differentselected component color light producing phosphors, a signal channel foreach selected component color representative signal train, anoscillator, the oscillator signal consisting of a number of phases equalin number to the number of diiferent selected component colors, meansfor modulating each of said layers and its corresponding component colorrepresentative signal trains with one phase of said oscillator outputsignal, and a connection between said intensity control electrode andall of said signal channels at a point in said signal channels whichincludes both the image signals and said oscillator signals.

9. In a color television system employing a plurality of simultaneoustype selected component color representative signal trains, a colorimage reproducing system comprising in combination a cathode ray tubehaving an electron gun for generating an electron beam,

an intensity control electrode for said electron beam,,

and a color producing electron target, a plurality of parallel layers ofdifferent selected component color light producing materials enclosed byand separated by electrically independent, conductive and transparentfilms, a signal channel for each selected component color representativesignal train, an oscillator having a substantially sinusoidal outputsignal, the oscillator signal also consisting of a number of phasesequal in number to the number of different selected component colors, asignal mixer in each of said signal channels, a connection between saidoscillator, each of said channels and its similarly color designatedcolor control electrode to apply one different phase to each of saidchannels and its similarly color designated color control electrode,said connections to said channels arranged to produce a mixing of theselected color component representative signal and said oscillatoroutput, and a connection between said intensity control electrode andall of said signal channels at a point in said signal channels whichincludes both the image signals and said oscillator signals.

References Cited in the file of this patent UNITED STATES PATENTS2,330,172 Rosenthal Sept. 21, 1943 2,335,180 Goldsmith Nov. 23, 19432,343,825 Wilson Mar. 7, 1944 2,416,056 Kallmann Feb. 18, 1947 2,423,769Goldsmith July 8, 1947 2,423,830 Fonda July 15, 1947 2,442,961 RambergJune 8, 1948 2,455,710 Szegho Dec. 7, 1948 2,461,515 Bronwell Feb. 15,1949 2,566,713 Zworykin Sept. 4, 1951 2,580,073 Burton Dec. 25, 1951

